Portable acoustic towers are generally used for choral and/or instrumental groups who perform in surroundings that, without the use of the acoustic tower or a group of acoustic towers, would not reflect the musical sound back to the performers to aid in coordination of the individual contributions to the performance. Such non-acoustical settings include auditoriums, gymnasiums and outdoor areas. Because these settings are non-traditional performance settings and, as such, are often used for non-performance activities, it is desirable that the acoustic tower not only be portable but also be easily stored in a minimal amount of space and provide the user with quick and easy set-up and take-down.
One of the first portable acoustic towers was developed by the Wenger Corporation and was patented in U.S. Pat. No. 3,180,446. This portable sound shell is disclosed as having two vertical members, or supports, to which is secured a vertical, first acoustic panel. A second acoustic panel is hingedly secured to the first panel and is provided with supports that allow the second panel to remain tilted relative the vertical panel and provide a canopy. Each of the vertical members is provided with a pair of folding feet which, when outstretched, provide stability for the sound shell. To transport the sound shell, the second panel is positioned in substantial vertical alignment with the first panel and the feet are folded inward. The whole sound shell may then be lifted and carried to a storage location. While this sound shell is of a straight-forward and useful design, the structure is not weighted and/or balanced to provide significant panel height and the necessity to actually lift and carry the sound shell, which can be quite heavy, creates a hardship on the user.
A later development in acoustic towers or shells, also by the Wenger Corporation, provides a mobile base and a tower with even more acoustic panels capable of reaching greater heights, see U.S. Pat. No. 3,630,309. This portable shell includes a frame structure with a rearwardly extending base incorporating a counterweight and four casters. Fixedly secured to the frame structure is a lower panel. A kicker panel is hingedly secured to the bottom of the lower panel; the kicker panel is rotated up and clipped in position for storage, and is unclipped and rotated downward for performance. An upper panel that has its own frame structure is hingedly secured to the frame structure of the lower panel. A canopy panel is hingedly secured, as by piano hinge, to the top edge of the upper panel. In a storage position, the canopy panel is folded close to the upper panel which rests substantially behind the lower panel. To reach performance position, the upper panel is raised and held in position with locking pins inserted into brackets such that the upper panel lies in substantial vertical alignment with the lower panel. The canopy panel is raised and secured at an angle, relative to the upper panel, by pulling downward on a pair of hinged rods that are connected to each side of the canopy panel and then securing a turnbuckle located on the ends of the rods to the frame structure.
The raising and lowering of all the panels in the portable acoustic shell described above, requires the physical maneuvering of the user, and perhaps is more efficiently handled with the physical maneuvering of two users due to the left and right side securement features required. For example, the upper panel and canopy panel must both be phsically lifted to a position the upper panel in substantial vertical alignment with the lower panel. While the upper panel is being held in an upright position, the user must hysically insert a locking pin in the frame structure to the left side of the acoustic shell. Once the upper panel is secured in position, one or two users must physically pull down on the rods connected to the canopy panel to raise it to a desired location. The user, or users, must then physically engage the turnbuckle to the frame structure on the right side of the acoustic shell and engage the turnbuckly to the foam structure on the left side of the acoustic shell to hold the position of the canopy panel. The canopy panel is provided with no means to measure the angle to which it is raised, rather the user must simply, by sight, judge the appropriate angle. Having no means to accurately and repeatably set the angle of the canopy panel requires numerous readjustments when attempting to arrange a number of the acoustic shells in a performance group.
U.S. Pat. No. 5,403,979, owned by Rogers et al., provides for a variation on the portable acoustic shell from that described above. This acoustic shell does not provide a canopy panel but rather comprises two substantially vertical panels. The lower panel is fixedly secured to a frame structure that stands atop a wheeled base. The upper panel lies in front of the lower panel at all times and includes a support structure that is telescopically secured to the frame structure of the lower panel. This support structure is provided with weighted handles that the user may press down upon or lift up upon to raise and lower, respectively, the upper panel relative the fixed lower panel. The weighted handles are weighted to substantially, exactly counterbalance the weight of the upper panel. In theory, the upper panel may be raised or lowered to any position and the exact balance of the counterweighted handles will maintain the upper panel in that position.
The acoustic shell described immediately above does not, as indicated, provide for a canopy panel and the enhanced sound acoustics it can provide. Further, while the upper panel is relatively easily raised and lowered, it always maintains its position, at least in part, in front of the lower panel; there is never vertical alignment of the panels and thus, never a full smooth panel for improved acoustics. Additionally, there is no manner in which to secure the position of the upper panel relative the lower panel. In an outdoor setting or even that of a gymnasium or auditorium there is provided no means to prevent the casual passer-by from lifting up or down on the handles and altering the position of the upper panel. Moreover, the stability and positioning of the upper panel relies completely on the substantially, exact balance of counterweights to the weight of the upper panel. Any alteration in the make-up of the panel, e.g. the panel absorbing water or the panel being otherwise damaged/modified, or in the make-up of the counterweight, e.g. damage to the counterweight, may alter this exact balance and prevent the ability of upper panel to maintain its position. Panel positions that are easily altered and/or difficult to maintain present a problem when attempting to group a number of acoustic shells. That is, not only do the unaligned panels present a sloppy and unprofessional appearance, but, the overall acoustic performance of the acoustic tower group may be significantly altered.
In view of the above, what is needed is a portable, multi-panel, acoustic tower whose panels are easily, and repeatably, raisable to a desired position by a single user. And, whose acoustic panels may be substantially secured in their position and protected from tampering. Further, with respect to the canopy panel, there is a need for a canopy panel that is easily and repeatably raisable to one of a number of predetermined angles, such that when a grouping of acoustic towers is presented a uniform and professional appearance is provided and acoustic performance is maximized. Additionally, as the portable, multi-panel, acoustic tower should provide for easy raising of its panels by a single user, it should also provide for easy lowering of its panels by a single user.